Halogen-free soldering flux and halogen-free soldering paste

Abstract

The invention provides halogen-free soldering flux and halogen-free soldering paste, and belongs to the technical field of electronic packaging materials. The halogen-free scaling powder comprises a corrosion inhibitor, an active agent and a solvent, the corrosion inhibitor is composed of sodium lauroyl sarcosinate and rutin, and the mass ratio of the sodium lauroyl sarcosinate to the rutin is (1-4): (1-4); the active agent is composed of organic acid and organic acid salt; the solvent is composed of a glycol ether solvent, an alcohol solvent and a terpene alcohol solvent; based on the mass of the halogen-free scaling powder, the mass percentage of the corrosion inhibitor is 1-3%; the mass percentage content of the active agent is 5-8%; the mass percentage content of the solvent is 30-45%. When the halogen-free soldering flux is added into the halogen-free soldering paste, the storage stability, the printing performance and the welding performance of the halogen-free soldering paste can be improved.

Description

Technical Field

[0001] This application relates to the field of electronic packaging materials technology, specifically to halogen-free flux and halogen-free solder paste. Background Technology

[0002] From a cost and reliability perspective, the bonding and assembly of electronic components to the substrates of electronic devices is mostly done using solder paste. One method for applying solder paste to the substrates of electronic devices is screen printing using a metal mask. In this case, the viscosity of the solder paste needs to be appropriately adjusted to ensure printability. However, the deterioration of the storage stability of solder paste causes its viscosity to sometimes increase over time. As the electronic packaging industry moves towards high density and miniaturization, solder paste is required to have a low void ratio at the solder interface in both micro-pitch and large-area soldering. Currently, the performance of solder paste can be improved by adding corrosion inhibitors, activators, and solvents. However, the above solutions have the following drawbacks: Although corrosion inhibitors can delay the corrosion of solder powder, they may excessively inhibit soldering activity, leading to cold solder joint defects. Increasing the activator content will accelerate the oxidation and deterioration of solder powder. Using strong activators will corrode the solder pad and produce solder balls. Using weak activators will increase the solder void ratio due to incomplete removal of oxides. High viscosity components in solvents can cause stencil clogging, and low boiling point solvents can cause the solder paste to evaporate and crack after continuous use, resulting in thermal collapse and bridging defects in fine-pitch printing. The above improvement methods cannot make solder paste balance storage stability, printability, and solderability. Summary of the Invention

[0003] The purpose of this application is to overcome the shortcomings of the prior art and provide a halogen-free flux and a halogen-free solder paste.

[0004] To achieve the above objectives, the technical solution adopted in this application is as follows: a halogen-free flux, comprising a corrosion inhibitor and an activator, wherein the corrosion inhibitor is composed of sodium lauroyl sarcosinate and rutin, and the mass ratio of sodium lauroyl sarcosinate to rutin is (1-4):(1-4); the activator comprises organic acids and organic acid salts; the solvent comprises ethylene glycol ether solvents, alcohol solvents, and terpene alcohol solvents; Based on the mass of the halogen-free flux, the corrosion inhibitor has a mass percentage of 1-3%; the activator has a mass percentage of 5-8%; and the solvent has a mass percentage of 30-45%.

[0005] In some embodiments, the organic acids include glutaric acid, succinic acid, stearic acid, adipic acid, benzoic acid, azelaic acid, eicosanoic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diethylene glycol, pyridine dicarboxylic acid, dibutylaniline diethylene glycol, caprylic acid, sebacic acid, thioglycolic acid, terephthalic acid, dodecanoic acid, p-hydroxyphenylacetic acid, pyridine carboxylic acid, phenyl succinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, and tartaric acid. At least one of the following: acid, tris(2-carboxyethyl)isocyanurate, glycine, 1,3-cyclohexanedicarboxylic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, 2,3-dihydroxybenzoic acid, 2,4-diethylglutaric acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, malic acid, p-anesic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, dimer acid, hydrogenated dimer acid, trimer acid, and hydrogenated trimer acid.

[0006] In some embodiments, the organic acid salt includes at least one of copper acetate, 1-ethyl-3-methylimidazolium methanesulfonate, triethanolamine sebacate, diethylamine adipate, and monocyclohexylamine glutarate.

[0007] In some embodiments, the activator is an organic acid and an organic acid salt, wherein the mass ratio of the organic acid to the organic acid salt is (3-5):(2-4).

[0008] In some embodiments, the activator is composed of glutaric acid, succinic acid and triethanolamine sebacate, wherein the mass ratio of glutaric acid, succinic acid and triethanolamine sebacate is (1-2):(2-3):(2.5-3.5).

[0009] In some embodiments, the mass ratio of the glycol ether solvent, alcohol solvent, and terpene alcohol solvent is (2.5–4.0):(3.5–5.0):(5.0–6.5).

[0010] In some embodiments, the halogen-free flux further includes the following components by weight percentage: 40-44% film-forming agent, 5-7% thixotropic agent, 3-5% lubricant, 1-2% stabilizer, and 0.2-0.4% antioxidant.

[0011] In some embodiments, the film-forming agent includes rosin-based resins.

[0012] In some embodiments, the antioxidant includes phenolic antioxidants.

[0013] In some embodiments, the thixotropic agent includes at least one of hydrogenated castor oil, castor wax, fatty acid derivatives, polymethyl methacrylate microspheres, and modified hydrogenated castor oil.

[0014] In some embodiments, the lubricant includes one of trimellitate, pentaerythritol ester, polyoxyethylene glycerol ether, monooctyl phosphate, white petrolatum, ethylene bis-stearamide, oleamide, and erucamide.

[0015] In some embodiments, the stabilizer includes at least one of polyethylene wax, ethyl cellulose, phosphite, and octadecylphosphonic acid.

[0016] In a second aspect, a halogen-free solder paste is provided, comprising the following components by weight percentage: 85-90% solder material and 10-15% flux.

[0017] Compared with the prior art, the beneficial effects of this application are as follows: The corrosion inhibitor in this halogen-free flux is composed of sodium lauroyl sarcosinate and rutin. When added to the halogen-free flux, the functional groups containing lone pairs of electrons, such as N and O, at one end of the corrosion inhibitor's structural formula form stable coordinate bonds with the empty orbitals of the metal. The long-chain molecules at the other end form a hydrophobic and tightly wrapped physical barrier on the metal surface, effectively preventing corrosive ions from contacting the solder material surface, improving the storage stability of the halogen-free solder paste, inhibiting the thickening effect of the halogen-free solder paste, and improving the printability of the halogen-free solder paste. Through the activation effect of organic acids and / or organic acid salts, it protects the solder material and the soldering interface, reduces oxide generation, lowers the surface tension of the solder material, and reduces the soldering void rate of the halogen-free solder paste. Attached Figure Description

[0018] Figure 1 This is a diagram showing the effect of flux on the welding void rate in Example 1; Figure 2 This is a graph showing the effect of flux on the welding void rate in Example 6; Figure 3 This is a diagram showing the effect of flux on the welding void rate in Example 7; Figure 4 This is a diagram showing the effect of flux on the welding void rate in Example 9; Figure 5 This is a diagram showing the effect of flux on the welding void ratio in Example 10; Figure 6 This is a diagram showing the effect of flux on the welding void rate in Example 11; Figure 7 This is a diagram showing the effect of flux on the welding void rate in Example 12; Figure 8 This is a diagram showing the effect of flux on the welding void rate in Example 13; Figure 9 The diagram shows the effect of flux in Comparative Example 5 on the weld void rate. Figure 10 This is a diagram showing the effect of flux in Comparative Example 6 on the welding void rate. Detailed Implementation

[0019] To facilitate understanding of this application, a more complete description will be provided below. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0020] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0021] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0022] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1-5” is disclosed, the described range should be interpreted as including ranges “1-4”, “1-3”, “1-2”, “1-2 and 4-5”, “1-3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0023] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0024] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has 'a' parts by mass and component B has 'b' parts by mass, it means that the mass ratio of component A to component B is a:b. It is important to understand that, unlike mass percentage content, the sum of the mass parts of all components is not limited to 100 parts.

[0025] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0026] A first aspect of this application provides a halogen-free flux comprising a corrosion inhibitor, an activator, and a solvent, wherein the corrosion inhibitor is composed of sodium lauroyl sarcosinate and rutin, and the mass ratio of sodium lauroyl sarcosinate to rutin is (1-4):(1-4); the activator comprises organic acids and organic acid salts; and the solvent comprises ethylene glycol ether solvents, alcohol solvents, and terpene alcohol solvents. Based on the mass of the halogen-free flux, the corrosion inhibitor has a mass percentage of 1-3%; the activator has a mass percentage of 5-8%; and the solvent has a mass percentage of 30-45%.

[0027] The corrosion inhibitor in this halogen-free flux is composed of sodium lauroyl sarcosinate and rutin. When added to the halogen-free flux, the N and O functional groups containing lone pairs of electrons at one end of the corrosion inhibitor's structural formula form stable coordinate bonds with the empty orbitals of the metal. The long-chain molecules at the other end form a hydrophobic and tightly wrapped physical barrier on the metal surface, effectively preventing corrosive ions from contacting the solder material surface, improving the storage stability of the halogen-free solder paste, and simultaneously inhibiting its tackifying effect, thus improving its printability. Through the activation of organic acids and organic acid salts, it protects the solder material and the soldering interface, reduces oxide generation, lowers the surface tension of the solder material, and reduces the solder void rate of the halogen-free solder paste. The solvent can alter the rheological behavior of the halogen-free solder paste, and combined with the corrosion inhibitor, further inhibits its tackifying effect and improves its printability.

[0028] Specifically, the mass ratio of sodium lauroyl sarcosinate to rutin can be one of the following or any combination of two: 4:1, 3.5:1, 3:1, 2.5:1, 2:1, 1.5:1, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, preferably (1.5 to 2.5):(2.5 to 3.5).

[0029] Specifically, based on the quality of the halogen-free flux, the mass percentage of the corrosion inhibitor can be a range of one or any combination of 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, and 3%.

[0030] Specifically, based on the quality of the halogen-free flux, the mass percentage of the activator can be 5%, 5.2%, 5.5%, 5.7%, 6%, 6.3%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.7%, or 8%.

[0031] Specifically, the mass percentage of the solvent can be a range of one or any combination of 30%, 32%, 35%, 37%, 39%, 41%, 43%, and 45%.

[0032] In some embodiments, the organic acids include glutaric acid, succinic acid, stearic acid, adipic acid, benzoic acid, azelaic acid, eicosanoic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diethylene glycol, pyridine dicarboxylic acid, dibutylaniline diethylene glycol, caprylic acid, sebacic acid, thioglycolic acid, terephthalic acid, dodecanoic acid, p-hydroxyphenylacetic acid, pyridine carboxylic acid, phenyl succinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, and tartaric acid. At least one of the following: acid, tris(2-carboxyethyl)isocyanurate, glycine, 1,3-cyclohexanedicarboxylic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, 2,3-dihydroxybenzoic acid, 2,4-diethylglutaric acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, malic acid, p-anesic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, dimer acid, hydrogenated dimer acid, trimer acid, and hydrogenated trimer acid.

[0033] In some embodiments, the organic acid salt includes at least one of copper acetate, 1-ethyl-3-methylimidazolium methanesulfonate, triethanolamine sebacate, diethylamine adipate, and monocyclohexylamine glutarate.

[0034] Specifically, triethanolamine sebacate is a compound of sebacate and triethanolamine, which can be prepared in-house or purchased commercially.

[0035] Specifically, the triethanolamine sebacate is prepared by acid-base neutralization reaction of triethanolamine and sebacate.

[0036] Specifically, the diethylamine adipate is prepared by an acid-base neutralization reaction of adipic acid and diethylamine.

[0037] Specifically, the monocyclohexylamine glutarate is prepared by acid-base neutralization reaction of glutaric acid and monocyclohexylamine.

[0038] Specifically, acid-base neutralization reaction refers to the process of reacting carboxylic acids and organic amines to form ammonium carboxylate salts; the carboxylic acid in this application refers to one of sebacic acid, adipic acid, and glutaric acid; the organic amine in this application refers to one of triethanolamine, diethylamine, and cyclohexylamine.

[0039] Specifically, when the carboxylic acid is either sebacic acid or adipic acid, and the organic amine is either triethanolamine or diethylamine, the molar ratio of the organic amine to the carboxylic acid is 2:1; when the carboxylic acid is glutaric acid and the organic amine is monocyclohexylamine, the molar ratio of the carboxylic acid to the organic amine is 1:1.

[0040] Taking glutaric acid as the carboxylic acid and monocyclohexylamine as the organic amine as an example, the reaction equation for the acid-base neutralization reaction is as follows: HOOC-(CH2)3-COOH+C6H 11 NH2→HOOC-(CH2)3-COO - NH3 + -C6H 11 .

[0041] Specifically, the step of the acid-base neutralization reaction of the carboxylic acid and organic amine to generate an ammonium carboxylate salt includes: After dissolving the organic amine in ethanol, a carboxylic acid was added under stirring to carry out a neutralization reaction. The product obtained from the reaction was placed in a vacuum drying oven and dried at a temperature of 60-80°C to obtain an ammonium carboxylate salt.

[0042] In some embodiments, the mass ratio of the organic acid to the organic acid salt is (3-5):(2-4). For example, it can be a range of values ​​consisting of one or any two of 5:2, 5:3, 5:4, 4:2, 4:3, 4:4, 3:2, 3:4.

[0043] In this application, the mass ratio of organic acid to organic acid salt is within the above range, which can continuously remove oxides in stages, and is beneficial to further reduce the soldering void rate of halogen-free solder paste.

[0044] In some embodiments, the activator is composed of glutaric acid, succinic acid, and triethanolamine sebacate, wherein the mass ratio of glutaric acid, succinic acid, and triethanolamine sebacate is (1-2):(2-3):(2.5-3.5); for example, it can be a range of one or any two of 1:2:2.5, 1.5:2:2.5, 2:2:2.5, 1:2.5:2.5, 1:3:2.5, 1:2:3, 1:2:3.5, 1:3:3.5, or 2:3:3.5; preferably (1.1-1.3):(2.4-2.6):(2.8-3.0).

[0045] In this application, the activator, composed of glutaric acid, succinic acid and triethanolamine sebacate, with the mass ratio of the three components within the aforementioned range, can generate welding activity at different temperature gradients during the welding process. This effectively protects the solder material and the welding interface during heating, accelerates wetting speed, and thereby reduces the solder void rate of halogen-free solder paste.

[0046] Specifically, examples of alcohol solvents include 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyn-2,5-diol, 2,3-dimethyl-2,3-butanediol, 1,1,1-tris(hydroxymethyl)ethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, and 2,2′-oxobis(methylene). Bis(2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, bis[2,2,2-tri(hydroxymethyl)ethyl] ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, erythritol, threitol, guaiacol glycerol ether, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyn-4,7-diol, tetrahydrofurfuryl alcohol, etc.

[0047] Specifically, examples of ethylene glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, diethylene glycol monohexyl ether, and tetraethylene glycol dimethyl ether.

[0048] Specifically, terpineol can be listed as a solvent for terpene alcohols.

[0049] In some embodiments, the mass ratio of the glycol ether solvent, alcohol solvent, and terpene alcohol solvent is (2.5–4.0):(3.5–5.0):(5.0–6.5), for example, it can be a range of one or any two of 2.5:3.5:5, 3.0:3.5:5, 3.5:3.5:5, 4:3.5:5, 2.5:4:5, 2.5:5:5, 2.5:4:5.5, 2.5:4:6, 2:4:6.5, 4:5:6.5; preferably (3.0–3.3):(4.0–4.5):(5.5–6.0).

[0050] In this application, the mass ratio of glycol ether solvents, alcohol solvents, and terpene alcohol solvents within the above-mentioned range can maximize the dissolution of each component of the halogen-free solder paste, forming a uniform medium and improving the printability of the halogen-free solder paste; it also allows the solvent to evaporate in a gradient during the cold and hot collapse test, making it less prone to bridging of fine-pitch solder joints.

[0051] To further improve the storage stability, printability, and soldering performance of halogen-free solder paste, the solvent in this application is composed of diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol, and terpineol.

[0052] In some embodiments, the halogen-free flux further includes the following components by weight percentage: 40-44% film-forming agent, 5-7% thixotropic agent, 3-5% lubricant, 1-2% stabilizer, and 0.2-0.4% antioxidant.

[0053] In this application, the addition of the above-mentioned components to the halogen-free flux is beneficial to improving the overall performance of the halogen-free flux. Specifically, the corrosion inhibitor and antioxidant eliminate free radicals, constructing a dual protection mechanism to further isolate or reduce the contact between corrosive ions and the solder material surface, while the combination with the stabilizer improves the storage stability of the halogen-free solder paste; the thixotropic agent can change the rheological behavior of the halogen-free solder paste, and combined with the corrosion inhibitor and solvent, further inhibits the thickening effect of the halogen-free solder paste, improving the printability and soldering performance of the halogen-free solder paste.

[0054] Specifically, the mass percentage of the film-forming agent can be a range of one or any combination of 40%, 40.5%, 41%, 41.5%, 42%, 42.5%, 43%, 43.5%, and 44%.

[0055] Specifically, the mass percentage of the thixotropic agent can be a range of one or any combination of 5%, 5.2%, 5.4%, 5.6%, 5.8%, 6%, 6.2%, 6.4%, 6.6%, 6.8%, and 7%.

[0056] Specifically, the mass percentage of the lubricant can be a range of one or any combination of two of the following: 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, and 5%.

[0057] Specifically, the mass percentage of the stabilizer can be a range of one or any two of the following: 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, and 2%.

[0058] Specifically, the antioxidant content by mass percentage can be a range of one or any combination of two of the following: 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, and 0.4%.

[0059] In some embodiments, the film-forming agent includes rosin-based resins.

[0060] Examples of rosin-based resins include, for example, resin rosin, wood rosin, and top-oil rosin, as well as derivatives obtained from resin rosin. Examples of derivatives include, for example, refined rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, and α,β-unsaturated carboxylic acid modified compounds (acrylated rosin, maleic rosin, fumaric rosin, etc.), as well as refined products, hydrides, and disproportionates of polymerized rosin, and refined products, hydrides, and disproportionates of α,β-unsaturated carboxylic acid modified compounds. These rosin-based resins can be used alone or in combination of two or more.

[0061] In some embodiments, the rosin resin includes at least one of fully hydrogenated rosin, hydrogenated rosin alcohol, disproportionated rosin, icy white rosin, aqueous white rosin, polymerized rosin, and α,β-unsaturated carboxylic acid modified compounds.

[0062] In some embodiments, the antioxidant includes phenolic antioxidants.

[0063] Examples of phenolic antioxidants include triethylene glycol ether-di(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate (antioxidant 245), N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], 2,2'-methylenebis(6-tert-butyl-p-cresol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], and 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. [Propionate], 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylphenylamino)-1,3,5-triazine, pentaerythritol tetratetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2-thiodiethylidene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoamide), diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, dibutylhydroxytoluene (antioxidant 264), etc.

[0064] In some embodiments, the thixotropic agent includes at least one of hydrogenated castor oil, castor wax, fatty acid derivatives, polymethyl methacrylate microspheres, and modified hydrogenated castor oil; In some embodiments, the lubricant includes one of trimellitate, pentaerythritol ester, polyoxyethylene glycerol ether, monooctyl phosphate, white petrolatum, ethylene bis-stearamide, oleamide, and erucamide; In some embodiments, the stabilizer includes at least one of polyethylene wax, ethyl cellulose, phosphite, and octadecylphosphonic acid.

[0065] In some embodiments, the method for preparing the halogen-free flux includes the following steps: After heating the solvent to 110-120℃, add the film-forming agent and stir at 100-110℃ and 100-200rpm until the film-forming agent is completely dissolved to obtain the first solution. The surfactant is added to the first solution and stirred for 0.5-1 h at a temperature of 100-110℃ and a speed of 150-200 rpm to obtain the second solution. Add corrosion inhibitor, lubricant, antioxidant and stabilizer to the second solution, and stir for 0.5-1h at a temperature of 90-100℃ and a speed of 150-200rpm to obtain the third solution; Add the thixotropic agent to the third solution and stir for 1.5-2 hours at a temperature of 45-55℃ and a rotation speed of 800-1200 rpm; cool to room temperature to obtain halogen-free flux.

[0066] In a second aspect, a halogen-free solder paste is provided, comprising the following components by weight percentage: 85-90% solder material and 10-15% flux.

[0067] The halogen-free solder paste of this application contains the above-mentioned flux, which can improve the storage stability, printability and reduce the solder void rate of the halogen-free solder paste.

[0068] Specifically, the mass percentage of solder material can be a range of one or any combination of 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%.

[0069] Specifically, the flux mass percentage can be one or any combination of 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%.

[0070] In some embodiments, the solder material preferably contains Sn or a Sn-based alloy. Sn or Sn-based alloys may contain unavoidable impurities.

[0071] Sn can be Sn (3N material) with a purity of, for example, 99.9% or higher, Sn (4N material) with a purity of 99.99% or higher, or Sn (5N material) with a purity of 99.999%.

[0072] Examples of Sn-type alloys include alloys composed of Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Ag-Cu-Ni-Co, Sn-In, Sn-Bi, Sn-Sb, and Sn-Pb alloys, as well as alloys containing the above compositions but with added As, Bi, Sb, Pb, Ag, Cu, In, Ni, Co, Ge, P, Fe, Zn, Al, and Ga. The Sn content in Sn-type alloys is not particularly limited, but can be greater than 40% by mass.

[0073] From the viewpoint of minimizing the difference between the liquidus temperature (TL) and the solidus temperature (TS) (ΔT = TL - TS), Sn and Sn-based alloys are preferably Sn, Sn-Cu alloys, or Sn-Ag-Cu alloys. By minimizing ΔT, even when solder paste containing, for example, the aforementioned solder materials is applied to the substrate of an electronic device and allowed to solidify, the solder paste can maintain the uniformity of the solder material's structure. As a result, the solder paste exhibits excellent reliability in terms of cycling characteristics, etc. Similarly, Sn-Cu alloys preferably contain more than 0.1% to 1.0% by mass of Cu (preferably 0.5 to 1.0% by mass), with the remainder being Sn. Likewise, Sn-Ag-Cu alloys preferably contain more than 0.35% to 3.5% by mass of Ag (preferably 1.0 to 3.5% by mass), more than 0.1% to 1.0% by mass of Cu (preferably 0.1 to 1.0% by mass), with the remainder being Sn. From the viewpoint of achieving excellent reliability by minimizing ΔT, the Ag content relative to the overall solder material is preferably 0.05–3.5% by mass, more preferably 0.1–3% by mass, and even more preferably 0.5–3% by mass. Furthermore, from the viewpoint of achieving excellent reliability by minimizing ΔT, the Cu content relative to the overall solder material is preferably 0.01–0.9% by mass, more preferably 0.05–0.75% by mass, and even more preferably 0.1–0.7% by mass. It is worth noting that the preferred numerical ranges for Ag and Cu content are independent of each other, and the Ag and Cu contents can be determined separately.

[0074] The Sn content relative to the total solder material can be, for example, 40% by mass or more, 50% by mass or more, 70% by mass or more, or 90% by mass or more. On the other hand, when the solder material contains Pb, the Pb content relative to the total solder material can be 90% by mass or more, and the Sn content relative to the total solder material can be 5% by mass or more, or 10% by mass or more. The solder material can contain, for example, 20 to 300 ppm by mass of As. By setting the As content to 20 ppm by mass or more, viscosity increase is suppressed, resulting in excellent adhesion suppression. By setting the As content to 300 ppm by mass or less, wettability degradation can be further suppressed. Therefore, by setting the As content to 20 to 300 ppm by mass, the solder paste of this embodiment can achieve a good balance between adhesion suppression and reliability. Based on the same viewpoint, the As content relative to the total solder material is preferably 30 to 250 ppm by mass, and more preferably 50 to 200 ppm by mass. As can form alloys with Sn or Sn-type alloys (e.g., intermetallic compounds, solid solutions, etc.), or it can exist independently of Sn-type alloys as, for example, elemental As or oxides. The solder material preferably contains 50 ppm (0.0050 wt%) to 3.0 wt% Bi. By setting the Bi content to 50 ppm or more, viscosity increase is suppressed, resulting in excellent viscosity-inhibiting effects. By setting the Bi content to 3.0 wt% or less, the difference between the liquidus temperature (TL) and the solidus temperature (TS) (ΔT = TL - TS) can be reduced, resulting in excellent reliability in cycling characteristics, etc. Therefore, by setting the Bi content to 50 ppm to 3.0 wt%, the solder paste of this embodiment can achieve a good balance between viscosity-inhibiting effects and reliability. Based on the same viewpoint, the Bi content relative to the overall solder material is preferably 50 ppm (0.0050 wt%) to 1.0 wt%, more preferably 100 ppm (0.010 wt%) to 1.0 wt%.

[0075] The solder material preferably contains 20 ppm (0.0020 wt%) to 0.5 wt% Sb. By maintaining an Sb content of 20 ppm or more, viscosity increase is suppressed, resulting in excellent anti-tackling effect. By maintaining an Sb content of 0.5 wt% or less, excellent reliability is achieved in areas such as wetting properties and cycling characteristics. Therefore, by maintaining an Sb content of 20 ppm to 0.5 wt%, the solder paste of this embodiment achieves a good balance between anti-tackling effect and reliability. Based on the same viewpoint, the Sb content relative to the overall solder material is preferably 50 ppm (0.0050 wt%) to 0.3 wt%, more preferably 100 ppm (0.010 wt%) to 0.1 wt%. The solder material preferably contains 20 ppm (0.0020 wt%) to 0.7 wt% Pb. By maintaining a Pb content of 20 ppm or more, viscosity increase is suppressed, resulting in excellent anti-tackling effect. By reducing the Pb content to 0.7% by mass or less, the difference between the liquidus temperature (TL) and the solidus temperature (TS) (ΔT = TL - TS) can be reduced, resulting in excellent reliability in terms of cycling characteristics. Therefore, by reducing the Pb content to 20 ppm to 0.7% by mass, the solder paste of this embodiment can achieve a good balance between adhesion inhibition and reliability. Based on the same viewpoint, the Pb content relative to the overall solder material is preferably 50 ppm (0.0050% by mass) to 0.5% by mass, more preferably 100 ppm (0.010% by mass) to 0.3% by mass. Bi can exist together with Sn or Sn-type alloys as an alloy (e.g., intermetallic compound, solid solution, etc.), or it can exist independently of Sn and Sn-type alloys.

[0076] The method for manufacturing the solder material in this embodiment is not particularly limited; for example, a method of manufacturing by melting and mixing raw material metals is listed.

[0077] In this embodiment, the form of the solder material is not particularly limited; for example, it can be in the form of wire, spheres (solder balls), powder (solder powder), or other granular forms. From the viewpoint of excellent flowability, the solder material is preferably in a granular form, and more preferably in a powder form.

[0078] Methods for manufacturing granular solder materials include, for example, the dripping method, in which molten solder material is dripped down to obtain particles; the spraying method, in which centrifugal spraying is performed; and methods for crushing lumpy solder material. In the dripping or spraying method, in order to form particles, the dripping or spraying is preferably carried out in an inert atmosphere or solvent.

[0079] Furthermore, when the solder material is in granular form, it is preferable that the solder material has a size (particle size distribution) belonging to number 1 to 8 in the powder size classification (Table 2) of JIS Z3284-1:2014, more preferably a size (particle size distribution) belonging to number 4 to 8, and even more preferably a size (particle size distribution) belonging to number 5 to 8. This allows for soldering to fine components.

[0080] In this embodiment, the size (particle size distribution) of the granular solder material can be determined by laser diffraction particle size distribution measurement test as described in 4.2.3 of JIS Z3284-2:2014.

[0081] In this embodiment, the solder paste may further contain zirconia powder. The content of zirconia powder relative to the total mass of the solder paste is preferably 0.05 to 20.0% by mass, more preferably 0.05 to 10.0% by mass, and most preferably 0.1 to 3% by mass. If the content of zirconia powder is within the above range, the activator contained in the flux preferentially reacts with the zirconia powder, and is less likely to react with Sn or Sn oxide on the surface of the solder powder, thereby further suppressing the increase in viscosity over time.

[0082] There is no upper limit to the particle size of the zirconia powder added to the solder paste, but it is preferably 5 μm or less. A particle size of 5 μm or less helps maintain the printability of the paste. Furthermore, there is no particular lower limit, but it is preferably 0.5 μm or more. The particle size mentioned above is the average of the projected circle diameters of particles with a projected circle diameter of 0.1 μm or more, obtained by taking an SEM image of the zirconia powder and using image analysis to determine the equivalent diameter of the projected circle for each particle present in the field of view. There is no particular limitation on the shape of the zirconia particles; different shapes increase the contact area with the flux, resulting in a thickening and inhibiting effect. Spherical shapes provide good flowability, thus achieving excellent printability as a solder paste. A suitable shape can be selected based on the desired characteristics.

[0083] In this embodiment, the solder paste can be manufactured by mixing the solder material (solder powder) and flux of this embodiment using a known method.

[0084] The solder paste of this embodiment is used for circuit boards with fine structures, such as those in electronic devices. Specifically, it can be applied to the soldering part by means of printing using a metal mask, dispensing using a dispenser, or transfer using a transfer needle for soft melting soldering.

[0085] Example 1 This embodiment provides a halogen-free flux comprising the following components by weight percentage: 42% film-forming agent, 6% thixotropic agent, 4% lubricant, 1.5% stabilizer, 0.3% antioxidant, 2% corrosion inhibitor, 6.6% activator, and the balance being solvent; wherein, The film-forming agent is Japanese Arakawa KE-604 hydrogenated rosin resin; The thixotropic agent is hydrogenated castor oil; The lubricant is glycerol polyvinyl ether G-18; The stabilizer is ethyl cellulose; The antioxidant is butylated hydroxytoluene, and the antioxidant is 264. The corrosion inhibitors are sodium lauroyl sarcosinate and rutin, with a mass ratio of sodium lauroyl sarcosinate to rutin of 2:3. The activators are glutaric acid and triethanolamine sebacate, with a mass ratio of glutaric acid to triethanolamine sebacate of 3.7:2.9; The solvents are diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol, and terpineol, with a mass ratio of 3:4:6.

[0086] The preparation method of the halogen-free flux in this embodiment includes the following steps: After heating the solvent to 110°C, the film-forming agent was added, and the mixture was stirred at 110°C and 200 rpm until the film-forming agent was completely dissolved to obtain the first solution. The surfactant was added to the first solution and stirred for 1 hour at 110°C and 200 rpm to obtain the second solution. The corrosion inhibitor, lubricant, antioxidant, and stabilizer were added to the second solution and stirred for 1 hour at 100°C and 150 rpm to obtain the third solution. The thixotropic agent was added to the third solution and stirred for 2 hours at 50°C and 1000 rpm. After cooling to room temperature, a halogen-free flux was obtained.

[0087] This embodiment also provides a halogen-free solder paste comprising the following components by weight percentage: 88.5% solder material and 11.5% halogen-free flux; wherein the solder material is SAC305.

[0088] The preparation method of halogen-free solder paste in this embodiment includes the following steps: adding solder material and halogen-free flux into a mixer and stirring at 300 rpm for 30 minutes to obtain halogen-free solder paste.

[0089] Example 2 Except for the mass ratio of sodium lauroyl sarcosinate to rutin in the halogen-free flux, which differs from that in Example 1, all other aspects are the same as in Example 1. In this example, the mass ratio of sodium lauroyl sarcosinate to rutin is 1.5:3.5.

[0090] Example 3 Except for the mass ratio of sodium lauroyl sarcosinate to rutin in the halogen-free flux, which differs from that in Example 1, all other aspects are the same as in Example 1. In this example, the mass ratio of sodium lauroyl sarcosinate to rutin is 2.5:2.5.

[0091] Example 4 Except for the mass ratio of sodium lauroyl sarcosinate to rutin in the halogen-free flux, which differs from that in Example 1, everything else is the same as in Example 1. In this example, the mass ratio of sodium lauroyl sarcosinate to rutin is 1:4.

[0092] Example 5 Except for the mass ratio of sodium lauroyl sarcosinate to rutin in the halogen-free flux, which differs from that in Example 1, everything else is the same as in Example 1. In this example, the mass ratio of sodium lauroyl sarcosinate to rutin is 4:1.

[0093] Example 6 Except for the activator in the halogen-free flux, which is different from that in Example 1, everything else is the same as in Example 1. In this example, the activator is glutaric acid, succinic acid and triethanolamine sebacate, and the mass ratio of glutaric acid, succinic acid and triethanolamine sebacate is 1.2:2.5:2.9.

[0094] Example 7 Except for the activator in the halogen-free flux, which is different from that in Example 6, everything else is the same as in Example 1. In this example, the activator is glutaric acid, succinic acid and triethanolamine sebacate, and the mass ratio of glutaric acid, succinic acid and triethanolamine sebacate is 1.1:2.6:2.8.

[0095] Example 8 Except for the activator in the halogen-free flux, which is different from that in Example 6, everything else is the same as in Example 1. In this example, the activator is glutaric acid, succinic acid and triethanolamine sebacate, and the mass ratio of glutaric acid, succinic acid and triethanolamine sebacate is 1.3:2.4:3.

[0096] Example 9 Except for the activator in the halogen-free flux, which is different from that in Example 6, everything else is the same as in Example 1. In this example, the activator is glutaric acid, succinic acid and triethanolamine sebacate, and the mass ratio of glutaric acid, succinic acid and triethanolamine sebacate is 1:3:3.5.

[0097] Example 10 Except for the activator in the halogen-free flux, which is different from that in Example 6, everything else is the same as in Example 1. In this example, the activator is glutaric acid, succinic acid and triethanolamine sebacate, and the mass ratio of glutaric acid, succinic acid and triethanolamine sebacate is 2:2:2.5.

[0098] Example 11 Except for the activator in the halogen-free flux, which is different from that in Example 6, everything else is the same as in Example 1. In this example, the activator is glutaric acid, succinic acid and 1-ethyl-3-methylimidazolium methanesulfonate, and the mass ratio of glutaric acid, succinic acid and 1-ethyl-3-methylimidazolium methanesulfonate is 1.2:2.5:2.9.

[0099] Example 12 Except for the activator in the halogen-free flux, which is different from that in Example 6, everything else is the same as in Example 1. In this example, the activator is glutaric acid, succinic acid and copper acetate, and the mass ratio of glutaric acid, succinic acid and copper acetate is 1.2:2.5:2.9.

[0100] Example 13 Except for the activator in the halogen-free flux, which is different from that in Example 6, everything else is the same as in Example 1. In this example, the activator is glutaric acid, fumaric acid and triethanolamine sebacate, and the mass ratio of glutaric acid, fumaric acid and triethanolamine sebacate is 1.2:2.5:2.9.

[0101] Example 14 Except for the mass ratio of diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol, and terpineol in the solvent of the halogen-free flux, which differs from that in Example 6, all other aspects are the same as in Example 1. In this example, the mass ratio of diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol, and terpineol is 3.3:4.5:5.5.

[0102] Example 15 Except for the mass ratio of diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol, and terpineol in the solvent of the halogen-free flux, which differs from that in Example 6, all other aspects are the same as in Example 1. In this example, the mass ratio of diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol, and terpineol is 2.5:5:6.5.

[0103] Example 16 Except for the mass ratio of diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol, and terpineol in the solvent of the halogen-free flux, which differs from that in Example 6, all other aspects are the same as in Example 1. In this example, the mass ratio of diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol, and terpineol is 4:3.5:5.

[0104] Example 17 Except for the solvent of the halogen-free flux, which is different from that in Example 6, everything else is the same as in Example 1. In this example, the solvent is diethylene glycol monomethyl ether, isopropanol and terpineol, and the mass ratio of diethylene glycol monomethyl ether, 1,2-butanediol and terpineol is 3:4:6.

[0105] Example 18 This embodiment provides a halogen-free flux comprising the following components by weight percentage: 40% film-forming agent, 5% thixotropic agent, 3% lubricant, 1% stabilizer, 0.2% antioxidant, 1% corrosion inhibitor, 5% activator, and the balance being solvent; wherein, The film-forming agents are disproportionated rosin and hydrogenated rosin alcohol, with a mass ratio of disproportionated rosin to hydrogenated rosin alcohol of 32:10; The thixotropic agent is modified hydrogenated castor oil; The lubricant is white petrolatum; The stabilizer is polyethylene wax; The antioxidant is butylated hydroxytoluene; The corrosion inhibitors are sodium lauroyl sarcosinate and rutin, with a mass ratio of sodium lauroyl sarcosinate to rutin of 2:3. The activators are glutaric acid and triethanolamine sebacate, with a mass ratio of glutaric acid to triethanolamine sebacate of 3.7:2.9; The solvents are diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol, and terpineol, with a mass ratio of 3:4:6.

[0106] This embodiment also provides a halogen-free solder paste comprising the following components by weight percentage: 85% solder material and 15% halogen-free flux; wherein the solder material is SAC305.

[0107] The preparation methods of the halogen-free flux and halogen-free solder paste in this embodiment are the same as those in Example 1.

[0108] Example 19 This embodiment provides a halogen-free flux comprising the following components by weight percentage: 44% film-forming agent, 7% thixotropic agent, 5% lubricant, 2% stabilizer, 0.4% antioxidant, 3% corrosion inhibitor, 8% activator, and the balance being solvent; wherein, The film-forming agent is hydrogenated rosin resin, Arakawa KE-604 from Japan; The thixotropic agent is hydrogenated castor oil; The lubricant is white petrolatum; The stabilizer is polyethylene wax; The antioxidant is triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], antioxidant 245; The corrosion inhibitors are sodium lauroyl sarcosinate and rutin, with a mass ratio of sodium lauroyl sarcosinate to rutin of 2:3. The activators are glutaric acid and triethanolamine sebacate, with a mass ratio of glutaric acid to triethanolamine sebacate of 3.7:2.9; The solvents are diethylene glycol monomethyl ether, tetrahydrofurfuryl alcohol, and terpineol, with a mass ratio of 3:4:6.

[0109] This embodiment also provides a halogen-free solder paste comprising the following components by weight percentage: 88.5% solder material and 11.5% halogen-free flux; wherein the solder material is SAC305.

[0110] The preparation methods of the halogen-free flux and halogen-free solder paste in this embodiment are the same as those in Example 1.

[0111] Comparative Example 1 Except for the corrosion inhibitor in the halogen-free flux, which is different from that in Example 1, everything else is the same as in Example 1. In this comparative example, the corrosion inhibitor is sodium lauroyl sarcosinate.

[0112] Comparative Example 2 Except for the corrosion inhibitor in the halogen-free flux, which is different from that in Example 1, everything else is the same as in Example 1. In this comparative example, the corrosion inhibitor is rutin.

[0113] Comparative Example 3 Except for the corrosion inhibitor in the halogen-free flux, which is different from that in Example 1, everything else is the same as in Example 1. In this comparative example, the corrosion inhibitors are sodium lauroyl sarcosinate and benzotriazole, and the mass ratio of sodium lauroyl sarcosinate to benzotriazole is 2:3.

[0114] Comparative Example 4 Except for the corrosion inhibitor in the halogen-free flux, which is different from that in Example 1, everything else is the same as in Example 1. In this comparative example, the corrosion inhibitor is sodium lauroyl sarcosinate and melamine, and the mass ratio of sodium lauroyl sarcosinate to melamine is 2:3.

[0115] Comparative Example 5 Except for the activator in the halogen-free flux, which is different from that in Example 1, everything else is the same as in Example 1. The activator in this comparative example is glutaric acid.

[0116] Comparative Example 6 Except for the activator in the halogen-free flux, which is different from that in Example 1, everything else is the same as in Example 1. The activator in this comparative example is triethanolamine sebacate.

[0117] Comparative Example 7 Except for the solvent in the halogen-free flux, which is different from that in Example 1, everything else is the same as in Example 1. The solvent in this comparative example is diethylene glycol monomethyl ether.

[0118] Comparative Example 8 Except for the solvent in the halogen-free flux, which is different from that in Example 1, everything else is the same as in Example 1. The solvent in this comparative example is tetrahydrofurfuryl alcohol.

[0119] Comparative Example 9 Except for the solvent in the halogen-free flux, which is different from that in Example 1, everything else is the same as in Example 1. The solvent in this comparative example is terpineol.

[0120] Performance testing 1) Storage stability: The halogen-free solder paste obtained in the examples and comparative examples was first tested for its initial viscosity value, which is A1 (viscometer: Malcom). Then, it was placed in a sealed environment at a temperature of 25±2℃ and a humidity of 45-55% for 20 days. Starting from the 21st day, the viscosity value was tested daily and recorded as A2. The change rate = (A2-A1) / A1*100%. A change rate of less than 10% was considered as the solder paste not deteriorating, and a change rate of greater than or equal to 10% was considered as the solder paste having deteriorated and failed. The number of days of failure and deterioration was recorded.

[0121] 2) Printing performance: 2.1) Continuous Printing Lifespan of the Stencil: The halogen-free solder paste obtained in the examples and comparative examples was continuously printed on a solder paste printer. The squeegee pressure was 3 kg, the printing speed was 50 mm / s, the squeegee angle was 45°, and the squeegee demolding speed was 1 mm / s. During the printing process, it was observed whether the solder paste on the squeegee could fall smoothly. If the solder paste could not fall smoothly, it was considered to have failed and printing could not continue. This duration is the continuous printing lifespan of the solder paste.

[0122] 2.2) Cold collapse and hot collapse: Cold collapse and hot collapse tests were conducted in accordance with the collapse test method in standard GB / T31475-2015 (solder paste for high-quality internal interconnection in electronic assembly); 3) Welding performance: The halogen-free solder pastes obtained in the examples and comparative examples were printed onto 50*30mm copper plates using a 48*28mm aperture and a 0.3mm thick stencil. Then, a 50*30mm copper plate was used to cover the halogen-free solder paste. The plates were then run through a reflow oven with reflow curves of room temperature - 150℃ for 40-80 seconds, 150℃ - 210℃ for 50-70 seconds, and 215-250℃ for 45-70 seconds. The solder void rate of the copper plate after reflow soldering was tested using an ultrasonic scanner; a lower solder void rate indicates better soldering performance.

[0123] The test results are shown in Table 1 and Figure 1-10 As shown.

[0124] Table 1 As can be seen from the experimental data in Table 1, the halogen-free solder paste of this application meets the following requirements: storage stability ≥ 25 days, continuous screen printing time ≥ 9.5 h, no bridging of spacing greater than 0.2 mm during cold collapse test, no bridging of spacing greater than 0.25 mm during hot collapse test, and solder void rate ≤ 16.5%. This indicates that the halogen-free solder paste of this application has excellent storage stability, printing performance, and soldering performance.

[0125] The experimental data from Examples 1-5 show that when the mass ratio of sodium lauroyl sarcosinate to rutin is (1.5-2.5):(2.5-3.5), the resulting halogen-free solder paste meets the following requirements: storage stability ≥30 days and continuous screen printing time ≥10 hours. This indicates that when the mass ratio of sodium lauroyl sarcosinate to rutin is (1.5-2.5):(2.5-3.5), the storage stability and printing performance of the halogen-free solder paste can be improved.

[0126] The experimental data from Examples 1 and 6-13 show that when the activator is composed of glutaric acid, succinic acid, and triethanolamine sebacate, and the mass ratio of glutaric acid, succinic acid, and triethanolamine sebacate is (1-2):(2-3):(2.5-3.5), the soldering void rate of the obtained halogen-free solder paste is ≤10.5%. This indicates that when the activator is composed of glutaric acid, succinic acid, and triethanolamine sebacate, and the mass ratio of glutaric acid, succinic acid, and triethanolamine sebacate is (1-2):(2-3):(2.5-3.5), the soldering performance of the halogen-free solder paste can be further improved.

[0127] The experimental data from Examples 1 and 14-16 show that when the mass ratio of glycol ether solvent, alcohol solvent, and terpene solvent is (3.0-3.3):(4.0-4.5):(5.5-6.0), the resulting halogen-free solder paste exhibits no bridging at gaps greater than 0.2 mm during cold collapse testing and no bridging at gaps greater than 0.25 mm during hot collapse testing. This indicates that a mass ratio of glycol ether solvent, alcohol solvent, and terpene solvent of (3.0-3.3):(4.0-4.5):(5.5-6.0) can improve the printability of halogen-free solder paste.

[0128] The experimental data from Examples 1 and Comparative Examples 1-9 show that when the corrosion inhibitor lacks sodium lauroyl sarcosinate or rutin, the activator lacks organic acid or organic acid salt, and the solvent lacks at least one of glycol ether solvent, alcohol solvent, and terpene alcohol solvent, the resulting halogen-free solder paste does not meet the following requirements: storage stability ≥25 days, continuous screen printing time ≥9.5h, no bridging of spacing greater than 0.2mm during cold collapse test, no bridging of spacing greater than 0.25mm during hot collapse test, and solder void rate ≤16.5%. This indicates that the lack of at least one component in the corrosion inhibitor, activator, and solvent in the halogen-free solder paste will lead to a decrease in at least one of the following properties: storage stability, printing performance, and soldering performance.

[0129] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of this application and not to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A halogen-free fluxing agent characterized by, The product includes a corrosion inhibitor, an active agent, and a solvent. The corrosion inhibitor is composed of sodium lauroyl sarcosinate and rutin, wherein the mass ratio of sodium lauroyl sarcosinate to rutin is (1-4):(1-4). The active agent contains organic acids and organic acid salts. The solvent contains ethylene glycol ether solvents, alcohol solvents, and terpene alcohol solvents. Based on the mass of the halogen-free flux, the corrosion inhibitor has a mass percentage of 1-3%; the activator has a mass percentage of 5-8%; and the solvent has a mass percentage of 30-45%.

2. The halogen-free flux according to claim 1, wherein The organic acids include glutaric acid, succinic acid, stearic acid, adipic acid, benzoic acid, azelaic acid, eicosanoic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diethylene glycol, pyridine dicarboxylic acid, dibutylaniline diethylene glycol, octanoic acid, sebacic acid, thioglycolic acid, terephthalic acid, dodecanoic acid, p-hydroxyphenylacetic acid, pyridine carboxylic acid, phenyl succinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, and tartaric acid. At least one of the following: tris(2-carboxyethyl)isocyanurate, glycine, 1,3-cyclohexanedicarboxylic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, 2,3-dihydroxybenzoic acid, 2,4-diethylglutaric acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, malic acid, p-anesic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, dimer acid, hydrogenated dimer acid, trimer acid, and hydrogenated trimer acid.

3. The halogen-free flux according to claim 1, wherein The organic acid salt includes at least one of copper acetate, 1-ethyl-3-methylimidazolium methanesulfonate, triethanolamine sebacate, diethylamine adipate, and monocyclohexylamine glutarate.

4. The halogen-free flux as described in claim 1, characterized in that, The mass ratio of the organic acid to the organic acid salt is (3-5):(2-4).

5. The halogen-free flux as described in claim 1, characterized in that, The activator is composed of glutaric acid, succinic acid and triethanolamine sebacate, wherein the mass ratio of glutaric acid, succinic acid and triethanolamine sebacate is (1-2):(2-3):(2.5-3.5).

6. The halogen-free flux as described in claim 1, characterized in that, The mass ratio of the ethylene glycol ether solvent, alcohol solvent, and terpene alcohol solvent is (2.5–4.0):(3.5–5.0):(5.0–6.5).

7. The halogen-free flux as described in claim 1, characterized in that, The halogen-free flux also includes the following components by weight percentage: 40-44% film-forming agent, 5-7% thixotropic agent, 3-5% lubricant, 1-2% stabilizer, and 0.2-0.4% antioxidant.

8. The halogen-free flux as described in claim 7, characterized in that, The film-forming agent includes rosin-based resins; and / or, the antioxidant includes phenolic antioxidants.

9. The halogen-free flux as described in claim 7, characterized in that, The thixotropic agent includes at least one of hydrogenated castor oil, castor wax, fatty acid derivatives, polymethyl methacrylate microspheres, and modified hydrogenated castor oil. And / or, the lubricant includes one of trimellitate, pentaerythritol ester, polyoxyethylene glycerol ether, monooctyl phosphate, white petrolatum, ethylene bis-stearamide, oleamide, and erucamide; And / or, the stabilizer includes at least one of polyethylene wax, ethyl cellulose, phosphite, and octadecylphosphonic acid.

10. A halogen-free solder paste, characterized in that, It comprises the following components by weight percentage: 85-90% solder material and 10-15% halogen-free flux as described in any one of claims 1-9.

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